Find the number of rows and columns of a given matrix using NumPy
The shape
attribute of a NumPy array returns a tuple representing the dimensions of the array. For a two-dimensional array, the shape tuple contains two values: the number of rows and the number of columns.
In this article, let’s discuss methods used to find dimensions of the matrix.
How to Find the Number of Rows and Columns of a Matrix?
We can find matrix dimension with three ways:
- Using shape Attribute
- Using Indexing
- Using numpy.reshape()
Way 1: Using .shape Attribute
Here we are finding the number of rows and columns of a given matrix using Numpy.shape.
Python
import numpy as np matrix = np.array([[ 9 , 9 , 9 ], [ 8 , 8 , 8 ]]) dimensions = matrix.shape rows, columns = dimensions print ( "Rows:" , rows) print ( "Columns:" , columns) |
Output:
Rows: 2
Columns: 3
Way 2: Using Indexing
Here we are finding the number of rows and columns of a given matrix using Indexing.
Python
import numpy as np matrix = np.array([[ 4 , 3 , 2 ], [ 8 , 7 , 6 ]]) rows = matrix.shape[ 0 ] columns = matrix.shape[ 1 ] print ( "Rows:" , rows) print ( "Columns:" , columns) |
Output:
Rows: 2
Columns: 3
Way 3: Using numpy.reshape()
Here we are using numpy.reshape() to find number of rows and columns of a matrix, numpy.reshape
in NumPy is used for changing the shape of an array without modifying the underlying data.
When using
np.arange(start, stop)
, remember that the stop element is not included in the generated array. So,np.arange(1, 10)
will create an array with values from 1 to 9 (inclusive).
Python
import numpy as np matrix = np.arange( 1 , 10 ).reshape(( 3 , 3 )) print (matrix) # Original matrix print (matrix.shape) # Number of rows and columns of the said matrix |
Output:
[[1 2 3]
[4 5 6]
[7 8 9]]
(3,3)
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